Hunting with a silencer: Ammo choice is key to a quiet gun

SPRINGVILLE, Alabama -- The Alabama Department of Conservation and Natural Resources Advisory Board ruled last Saturday that Alabama hunters can use a silencer on their hunting firearms next season. Over 30 states currently allow this practice and I applaud the decision.

When I got mine, I tried several different types of .22lr ammo and found there was a huge difference in sound level depending on what velocity ammo I used. Lower velocity rounds worked much better. The magic for my rifle/suppressor combo was between 1025 fps and 1100 fps. When I used a round that was of a high velocity the crack of the report was very evident.

The way a silencer works is pretty simple. The silencer housing is made up of either aluminum or steel with a series of baffles on the inside and holes or exhaust ports on the outside end. The silencer or "can" as they are sometimes called, has a volume that is 20-30 times larger that the barrel itself. This allows the exhaust gases from the gunpowder exploding in the barrel to expand into the much larger chamber of the silencer and "slow down" and decease the gas pressure. Lower gas pressure exiting the barrel means less noise at the muzzle.

So, what does bullet velocity have to do with all this? Anything traveling at a supersonic speed breaks the sound barrier, causing a boom or a "crack". If a bullet is traveling above a certain speed, it becomes supersonic. High gas pressure at the muzzle also adds noise. Dispersing the exhaust gas helps to quiet the noise at the muzzle as the bullet exits.

In the video, I used a standard Federal high velocity round rated at 1260 fps and a CCI standard velocity round rated at 1050 fps. I shot both rounds without the silencer and both with the silencer. The difference in noise at the muzzle is substantial. Lower the exit velocity by just 210 fps silenced the round. The only sound came from the bolt cycling the round in the gun.

All silencers will reduce muzzle sound to some degree, but velocity is the most important part of the equation. Other popular rounds that work with suppressors really well are .45ACP and 9 mm. The .45ACP is a heavy (185-230 grain) bullet that travels at a very slow 800-950 fps. Silencers perform very well with this round because of the lower velocity. In a pistol, the 9mm round works well with a silencer because the bullet leaves the barrel so fast it doesn't have time to reach a supersonic velocity. Remember silencers only stop sound at the firearm, not down range.

One other thing about a silencer/suppressor is, due to the fact that sound is lowered at the muzzle, it is harder to tell from what direction the shot was fired. Even if the bullet reaches supersonic speed, there is no way to tell from which direction to shot came from.

Other things that affect sound suppression are the length of the barrel, humidity, temperature and altitude. I'm not a scientist so here is a useful